Motor-control system.



H. L. BEACH. MOTOR CONTROL SYSTEM.

APPLICATION FILED OCT. 23, IJIS.

1,168,048. A Patented Jan. 11, 1916.

- WITNESSES: LEVENTOR [A ATTORNEY UNITED STATES PATENT oirnicn. I

HOWARD L. BEACH, pr EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELEGTRIQ AND MANUFACTURING COMPANY, CORPORATION OF PENNSYL:

VANIA.

MOTOR-CONTROL sYs'rEM.

Application filed October 23,1913. Serial No. 796,831. 1

gheny and State of Pennsylvania, have invented a new and useful Improvement in Motor-Control Systems, of which the following is a specification.

My invention relates to motor control sys-v tems, and it has particular reference to systems which employ dynamic braking for the purpose of bringing motors to rest.

My invention has for its object to provide a simple and eflicient means whereby dynamic braking may be effected automatically to bring motors to rest safely and quickly.

I have provided a system in which dynamic braking occurs automatically when the controller is moved to its off position.

Current-limit devices are employed to automatica-lly control the dynamic braking circuit during the period of bringing the motor to rest. An advantage of my system is that no mechanical operation required except the usual movement of the ontroller to open and close the motor circuit. Since the system is entirely automatic in its operation, the attention and loss of time required for manual operation are avoided. The currentlimit devices insure that the desired maximum breaking current will be employed to bring the motor to rest in the minimum time consistent with safety.

In the accompanying drawings, the single figure is a diagrammatic view of circuits and apparatus embodving my invention.

Current is supplied from line conductors land 2 through two-pole double throw electromagnetic switches 3 and 1 to a motor 5 that is to be controlled. The motor comprises an armature, indicated at (3, and a shunt field winding 7 that is controlled by a resistor 8.

A short circuit for the resistor 8 is controlled by two: electromagnetic switches 9 and 10 comprisingactuating coils 11 and 12 which are included in the dynamic braking circuit of the motor. The coil 12 is also in series with the motor armature during the normal operation of the motor. The coil 11 is preferably adjusted to allow the switch 9 to open at a low-current Value. The coil 12 :is arranged to open when the armature current reaches a Value slightly above that of normal full-load current.

\ A sectional starting resistor 13 is con- Patented. Jan. 11, 1916 trolled by-successively actuated electromagnetic switches 14,15, 16 and 17 which are connected to intermediate points of the resistor. .The switch 14 is provided with a coil 18 which serves both as an actuating and as a holding coil. Each of the switches 15, 16 and 17 is provided with an actuating coil 19 which is in series with the preceding switch and with a holding coil 20 which isv in series with its own contact terminals.

A controller 21 controls the direction of rotation of the motor through the electrol magnetic switches 3 and 4. The switches 3 and 4t comprise shunt actuating coils 22 and 23 and series holding coils 24:a'nd 25 which are included in the dynamic braking circuit. As illustrated, the controller is shown in its oil' or inoperative position. In starting the motor, the controller is moved to the right or to the left, according to'the direction in which it is desired to ro-' tate the motor. Assuming that the controller is moved to the right so that a contact segment 26 bridges the two lower contact fingers 27, the coil 23 is energized to close the switch 4; and complete a circuit which extends from the line conductor 1:, through the switch arm 28, coil 12, armature,6, switch arm 29, coil 18 and resistor 13'to line conductor 2. The coil 18 is thus en-' ergized to close the switch 14 and thereby complete a short circuit for one section of' the resistor 13 through the actuating coil T9 of the switch 15. The switches 15, 16, and 17 will then close in succession to short circuit the corresponding sections of the resistor 13. The holding coils 20 of the switches 4 I 15 and 16 will maintain the closure of the respective switches until the succeeding switch has closed. The closing of the switch 17,

however, connects its holding coil 20 in series with a short circuit for the entire resistor 13, thus insuring that the. resistor will be cut out during the operation of the motor under load. When the controller is thrown to the ofi' position, as illustrated, the coil 23 is deenergized and the switch 4: operates, by force of gravity, to open the motor-op crating circuit and to close a dynamic braking circuit which extends from the armature 6 through the coil 12, switch arm 30, coil 25, brake resistor 31, coil 11, coil 24'and switch arni 32, back to the motor armature. The coil 11, which is thus energized, closes and a resistor 1' ing circuit for contri.

cult.

the switch i t the field res the field of the motor. in case the braking current reaches a predetermined value which may be slightly above normal full load value. the coil 12 is s'uliiciently energized to open the sui ,h 10 and hrealt the short circuit for the resistor 8. (he motor field is thus wcal iencd and the breaking: current is correspondni r y decrease l. l en the current falls below the predetermined value for o 'iei'iing the switch 10, the latter closes. The oscillation the switch 10 occurs as long as the breaking current tends to exceed the value for which the coil 12 is adjusted. The breaking current thus kept within such limits that the motor is brought to rest as quickly as consistent with safety. iVhen the controller 21 is moved to either of its operating positions, the dynamic braking circuit is broken by the switch arm 30 or the switch arm the case may be.

I claim as my invention:

It. in a motor control system, the comhination with a motor haviiuz a field windine', and a resistor for controlling said winding, of a short circuit for said resistor, and current-limit devices operable at (lii'l'erent predetermined alu s for controlling said circuit.

2. in motor control system, the combination was; a. motor having a field Winding, and a resistor tor controlling said Winding, 01' a dynamic braking circuit for said 1110- tor, and means for shooting; said resistor when the current traversing said circuit exceeds a predetermined value and is less than a second. and higher predetermined value.

' 3. In a motor control. system, the combination Witha m tor having a field winding,

mn'lrolling'said ayii'iding, of a. dynamic lira 'ing; circuit comprising means actuat rent precletermined current rahu roiling said resistor.

41. srst-iim, the coml'iii'iaa; a iicld whirling, a. mid winding, and a r, of a dynamic motor, and means ermired maximum and opcraikc at minimum in of at; said shunt cir- 5. In a motor control system, the comhination with a. motor having; a hold wnuling, or a resistor in. series with said winding, a

a short circuit for.

cinircnt in said brak-v dynamic braking circuit ior said motor,

means for automatically closing said lu'alcing circuit when the operating circuit is opened, and means controlled by prog'res sively higher n-cdclerminod current values oi said braking circuit for closing and opening a shunt circuit for said iicld wind- 7. In a motor control system, the combination with a motor, an operating circuit. and a dynamic lu-ali'iug' circuit, of means for connecting said motor in one o'l said circuits and, at the same time, discomu-cliiug the motor from the other circuit, and means comprising -.urr\ nl-limit devices o u-rahle at. dillcrcnt prcdciormined rah. i or controh line the current values in said dynamic hrakin circuit.

8. In a, motor control system, the combination. with a motor having a field Winding, of a dynamic braking circuit "for said motor, means 'lor controllimi said ticld winding comprising a plurality of magnet switches having coils included in said hraliingr circuit, one of said coils hcin arranged to opcrate at a higher current value than the other.

5). In a motor control system, the'comhinzr tion with a motor having a iicld i-Yinding,ol. a resistor in series with said whirling, a shunt circuit for said resistor, a dynamic braking circuit for said motor, a plurality oi electromagnetic SYVltClitS ha ring coils in said braking circuit, one oi said switches being arranged to closesaid shunt circuit at a predctermincd current value, and a srcond switch being); arranged to open said shunt HOWARD L. l; l] A (Lil.

lVitnesses:

G110. \V. Ulnar, B. B. llijunsfi ill) 

